Homeowners in coastal Orange County are among the latest to discover this quirk. Signals from Naval Weapons Station Seal Beach have been interfering with remote openers as far as half a mile away.

Not because of any grand conspiracy theory, but rather the mundane use of a radio frequency the military hadn't used much before.

Homeowners in coastal Orange County are among the latest to discover this quirk. There, signals from Naval Weapons Station Seal Beach have been interfering with garage door openers as far as half a mile away since March.

That's when testing began on a new radio system that will allow the base to network with local fire and police agencies during emergencies. The frequency falls in the range of 380-399.9 megahertz, a band long reserved for the Department of Defense but rarely used.

"We hadn't had the need to use these frequencies before. As a result, garage door manufacturers began using them because they were pretty quiet," said Gregg T. Smith, a spokesman for the Navy station. "With the explosion of communications technology over the past 20 years, the DOD has been squeezed to use bands it didn't need to use before."

Reports of interference with garage door openers near military installations have been reported from Rhode Island to San Diego to Hawaii.

"Out of the blue, the garage door just stopped working," said Bill Davey, 51, of Norco. "We changed all the batteries in the remotes. When it still didn't work, it was like 'What's going on here?'"

The culprit was a Navy installation a quarter-mile away.

The Federal Communications Commission allows the so-called unlicensed use of frequencies for low-power purposes such as garage door openers and vehicle key fobs as long as they don't interfere with government communications systems, Smith said.

Smith said he's fielded 16 complaints from people near the Seal Beach base, but he assumes the interference is affecting many more. People can buy a device to retrofit their openers to another frequency; Davey's cost $60.

"Once you explain how it all works, folks aren't happy, but they've been understanding," Smith said.